fireblocks-webhooks

Fireblocks Webhooks

When to Use This Skill

• How do I receive Fireblocks webhooks?
• How do I verify the Fireblocks-Webhook-Signature header?
• Why is my Fireblocks webhook signature verification failing?
• How do I handle transaction.created or transaction.status.updated events?
• How do I validate a Fireblocks detached JWS (RS512) against the JWKS endpoint?

Verification (core)

Fireblocks Webhooks v2 signs every request with a detached JWS (RS512, RSA + SHA-512) in the Fireblocks-Webhook-Signature header. The header is a compact JWS with an empty payload segment (<protected-header>..<signature>). To verify, reinsert the raw request body (base64url-encoded) as the payload, then verify against the auto-rotated regional JWKS (https://keys.fireblocks.io/.well-known/jwks.json). Use the raw body bytes — never JSON.parse first.

import { createRemoteJWKSet, compactVerify } from 'jose';

const JWKS = createRemoteJWKSet(
  new URL('https://keys.fireblocks.io/.well-known/jwks.json')
);

// signatureHeader = value of the `Fireblocks-Webhook-Signature` header (detached JWS)
export async function verifyFireblocksWebhook(rawBody, signatureHeader) {
  const [header, , signature] = signatureHeader.split('.');   // header .. signature
  const payload = Buffer.from(rawBody).toString('base64url');  // raw body as JWS payload
  const fullJws = `${header}.${payload}.${signature}`;
  const { payload: verified } = await compactVerify(fullJws, JWKS, {
    algorithms: ['RS512'],                                     // pin alg (no alg confusion)
  });
  return JSON.parse(Buffer.from(verified).toString('utf8'));   // { id, eventType, data, ... }
}

For complete handlers with route wiring, event dispatch, and tests, see:

• examples/express/
• examples/nextjs/
• examples/fastapi/

Legacy (Webhooks v1): the older Fireblocks-Signature header (base64 RSA PKCS#1 v1.5 over the SHA-512 hash of the raw body, verified against a static per-environment PEM key) reached its migration deadline on March 20, 2026. New integrations should use the v2 JWKS scheme above. See references/verification.md for the legacy path.